Method for molding workpieces



9 mm, -WALTER ERNST Feb.- 18, 1941. w. ERNST METHOD FOR MOLDINGWORKPIECES Original Filed Aug. 16, 1938 2 Sheets-Sheet 1 Feb. 18, 1941.w. ERNST METHOD FOR MOLDING WORKPIECES Original Filed Aug. 16, 1938 2Sheets-Sheet 2 WALT! R ERNST:

Patented Feb. 18, 1941 UNITED STATES PATENT OFFICE METHOD FOR MOLDINGWORKPIECES Original application August 1c, 1938, Serial No. 225,156.Divided and this application April 6,

1939, Serial No. 266,393

2 Claims. 1 (01. 18-55) This invention relates to hydraulic controlsystems and methods of pressing workpieces and a method of pressing suchworkpieces with multiple pressures.

Another object is to provide a method of molding workpieces consistingin applying a moderate pressure to the material while the materialsoftens and partially conforms to the shape of the mold and thereafterto apply a higher pressure to the material to force the softenedmaterial into the remaining portions of the mold, this being especiallyvaluable in the case of complicated or intricate shapes of molds.

Another object is to provide a method of molding workpieces consisting,as described immediately above, wherein the initial pressure is appliedfor a predetermined period of time, at the expiration of which thehigher pressure is then applied automatically.

This application is a division of my application, Serial No. 225,156,filed August 16, 1938.

In the drawings:

Figure 1 is a transverse section through a radial pump embodying theadjustable high and low pressure control of this invention; and

Figure 2 is a diagrammatic View, partly in section, of a hydraulic presscontrol circuit utilizing the adjustable high and low pressurecontrolled radial pump of this invention.

In general, the adjustable high and low pressure control for radialpumps of this invention consists of a means for adjustably shifting thepressure control, such as the shift ring of the pump, to a plurality ofdifferent stages so that the pump may deliver pressure fluid up to acertain predetermined pressure and then shift to its neutral or nodelivery position, after which time it may again be placed upon deliveryup to the attainment of a new and diiferent pressure level, whereupon itagain shifts to its neutral or no delivery position.

Referring to the drawings in detail, Figure 1 shows a pump having acasing It] with pads having fiat surfaces |2 forreciprocablysupportapplication matured into United States Patent No. 2,159,553,dated May 23, 1939.

The shift ring I3 is provided with diametrically disposed bosses 30,having threaded sockets 3| for the reception of the shift rods 32 and33, respectively, passing through bores 34 and 35 in the pump casingIll. The bores 34 and 35 are provided with leakage chambers 36 havingleakage passageways 31 leading back to the interior of the casing H1.The pump casing I0 is provided with side portions 38 and 39, containingthe bores 34 and 35 and having flattened end surfaces 40 and 4|,respectively. Clamped against the end surface 40, as by the screws 42,is the corresponding surface 43 of the servomotor casing 44. The lattercontains a cylinder bore, generally designated 45, and having threeportions 46, 41 and 48. The cylinder bore 45 is closed by a cylinderhead 49 secured by the screws 50 to the servomotor casing 44.

Reciprocable within the cylinder bore 45 is a stepped piston head,generally designated 5|. The latter is mounted upon the shift rod 32 andlimited in its position thereon by the head 52 and the collar 53.Leakage escaping past the piston head 5| drains back into the interiorof the easing ID by way of the passageways 54 and 55 in the shift rod32, and thence by way'of the longitudinal passageway 56, through thepiston head 5|, into the chamber 36 and pasageway 31. The collar 53 isprovided with a conical end 51 co operating with a similar conicalsurface 58 in the piston head 5|. The latter is provided with portionsof different diameters, with annular shoulders or piston areas 59 and 60therebetween. The piston area 59 opens into a chamber 6| with a port 62leading thereto, whereas the piston area 6|] opens into a chamber 63having a similar port 64 leading thereto. Longitudinal passageways 65and 66 lead from the ports 62 and 64 to the end ports 61 and 68,respectively. The ports 67 and 68 are threaded so that they may beclosed by means of threaded plugs. The provision of the piston areas 59and GI] enables the exertion of different thrusts against the pistonhead 5| because of the difference in the areas of these annular pistonsurfaces.

Secured to the flat surface 4! of the side portion 39, as by the screws69, is the control casing II. The control casing II is provided with aslot II within which a yoke i0 is arranged to slide. The control casing'II is also provided with a cylindrical bore I2, having therein asliding sleeve I3 for receiving a coil spring M. One end of the latterbears against the yoke I0 and the other end against the internal flangeI5, having on its opposite side the collar I6 and ball thrust bear. ing'I'I engaged by the hub it of a hand wheel I9. The latter is providedwith a threaded bore 88 engaging the threaded end 8I of the shift rod 33and locked in any desired position by the locknut 82. A retaining nut 83is mounted on the extreme end of the threaded end 8!. By rotating thehand wheel IS the coil spring M may be caused to engage the flange I5 ofthe sleeve I3 with varying pressure, which is transmitted, through theshift rod 33, to the pump shift ring I3, and opposed by one of thepiston areas upon the servomotor piston head 5!.

The control casing II is likewise provided with a pair of cylinder bores8d having communicating ports and 86 at opposite ends thereof.Reciprocable in the cylinder bores 84 are piston heads 3'! with pistonrods 83 threaded therein, as at 89. The opposite ends of the piston rods88 are threaded into the sockets of the yoke Iii. Surrounding the pistonrods 83 are the packings 9i, compressed by the glands 92 for the purposeof preventing leakage. The cylinder bores 84 are closed at theiropposite ends by the cylinder heads 93, having apertures 94 throughwhich pass the stop rods 95, the opposite ends of which are threaded asat 96 into the ring 91. The latter is, provided with a ridge 98 engaginga corresponding groove 99 in the hub I08 of a hand wheel IdI. The hubI39 is threaded internally, as at I52, and engages the threaded portionsHi3 upon the outer surface of the control casing II. When the hand wheelI3! is rotated, the stop rods $5 are advanced into or withdrawn from thechambers within the cylinder bores 84, thereby providing adjustableabutments against which the piston heads 8! will come to rest when thepressure fluid is supplied thereto through the ports 86. Oil seals I94prevent leakage around the stop rods and are held in position by theretainers I05.

The radical pump and its associated control mechanism shown in Figure 1may be utilized in a variety of circuits. One such circuit is shown inFigure 2, and consists of the pump, generally designated I06, with itsservomotor, generally designated I01, and control device, generallydesignated I538. The casing III- of the pump I06 is provided with endplates I09, to one of which is secured the fluid outlet connection III]having a pressure connection III and a. suction connection IIZ. Asuction pipe II3 runs downwardly from the suction connection I I2, intothe interior of a fluid tank II I. Running from the pressure connectionIII is a pipe H5 leading to a four-way valve, generally designated IIB,from which the lines Ill and H8 lead respectively to the ports Ii!) andI20 at the opposite ends of the main cylinder I2I of a hydraulic press,generally designated I22. This press is represented diametrically, andcontains a piston I23 with a piston rod I26, these being reciprocablewithin the cylinder bore I25 within the main cylinder I 2!. Thehydraulic press I22 is provided with a frame I 2% connecting the maincylinder IZI with the press bed I2I, upon which the workpiece or die issupported. The piston rod I24 is provided with an arm I28, arranged tooperate a limit switch, in a manner subsequently to be described.

The four-way valve H5 is of a conventional type, and consists of acasing I30 having a bore I3I, within which reciprocate the valve headsI32 and I33 on the valve rod I34. At the end of the latter is a handleI35, shown diagrammatically as a ball, but alternatively consisting of alever or any other suitable means of shifting the valve rod I34. Thecasing I3il is provided with a central port I36 for the connection ofthe pump pressure line H5, and end ports I37 and I38 from which theexhaust line we runs to the tank Ii I. Also provided are twointermediate ports I40 and NH, from which the lines Ill and H8 leadrespectively to the main cylinder ports H9 and I28, as previouslystated. By shifting the valve rod I34 and its heads I32 and I33, theflow from the pump, through the pump pressure line H5, may be directedeither to the upper or lower part of the main cylinder I2I, while theopposite side thereof is connected to the exhaust line I39, in themanner well known to those skilled in the art. Thus, the shifting of thefour-way valve IIB controls the distribution .of pressure fluid from thepump to the press I22 in order to advance or retract the piston I23 andits piston rod I2l.

The portion of the hydraulic circuit by which the pump and servomotorcontrol systems are operated includes a three-way valve I 32, of aconventional type, and having a valve rod I43, terminating in thearmature Hi4 adapted to be shifted by the energization of the solenoidI45. The latter is connected to an electrical circuit, in a mannersubsequently to be described. From the three-way valve I42, the exhaustconduit I46 leads downwardly to the fluid tank II4, whereas the pressureconduit I41 leads to the ports 85 at the righthand ends of the cylinderbores 84 (Figure 1), from the opposite ends of which the exhaust line M8leads downwardly to the fluid tank IN. The three-way valve I 52 issupplied by pressure fluid through the conduit I49 leading to it fromthe pump pressure fluid line H5, a branch conduit I5 3 proceeding to oneor both of the ports 62 or 64 in the servomotor casing (Figure 2).

The servomotor IIil may be caused to become operative and shift theshift ring I3 of the pump I06 to its neutral or no delivery position atany one of three predetermined pressures for the same setting of thethrust of the coil spring 'I l (Figure 1). These three differentpressures are determined by the area on the servomotor piston head 5i,which is subjected to a pressure fluid reaching it from the conduit I50.If both of the annular piston areas 59 and 60 in the chambers GI and 63are subjected to this pressure fluid, then the maximum area of theservomotor piston EE is in use, and a relatively low pressure in theconduit I50 will cause the servomotor piston EI' to shift and overcomethe thrust of the coil spring 74 in order to place the pump shift ringI3 in its neutral or no delivery position. If the annular piston area 59alone is subjected to this pressure fluid, then an intermediate pressurewill be required to overcome the thrust of the coil spring 14 and placethe pump in its no delivery position. If, however, the smaller annularpiston. area 60 is alone subjected to this pressure fluid, then arelatively :1)", carrying with them the yoke 10 and further highpressure in the conduit I50 will be required to overcome the thrust ofthe coil spring 14 and shift the pump shift ring I3 to its neutral or nodelivery position.

To utilize both piston areas 59 and 60 the ports 61 and 68 are unpluggedwhile the port 62 remains plugged, thereby establishing a connectionbetween the chambers 63 and 6| by way of the longitudinal bores 66 and65. If the larger annular piston area 59 is to be utilized, the conduitI50'is connected to the port 62, and the ports 51, 68 and 64 areplugged. If, however, the smaller piston area 60 is to be utilized, theports 61, 68 and 62 are plugged, in the manner shown in Figure 2.

The electrical circuit for energizing the solenoid I45 includes thelines II and I52, leading to the contractor I53 having normally openswitch blade-s I54 and I55, adapted when closed to connect the lines I5i and I52, respectively, With the power lines I56 and I51. Theoperating coil I58 of the contactor I53 is connected, by the lines I59and I60, to the timing device I 6| from which the lines I62 and I63lead, respectively, to the power line I51 and to the normally open limitswitch I64. The limit switch I64 is adapted to be closed by the pressarm I28 when it reaches a predetermined position, thereby connecting theline I63, through the limit switch I64, to the line I65 leading to thepower line I56. The spring I66 normally opens the limit switch I64 whenthe press arm I28 is retracted.

Operation In the operation of the circuit shown in Figure 2, let it beassumed that a relatively high pressure is desired to shift the pumpshift ring I3 to its neutral position so that the connections of theservomotor I01 are as shown in Figure 1. The smaller annular piston area60 is therefore utilized for this purpose, and subjected to the pressurefluid in the conduit I50. The hand wheel is then turned until the coilspring 14 is given the desired thrust so that, for example, a pressureof 500 poundsper square inch is required at the annular piston area 60to compress the coil spring 14 and move the pump shift ring I3 to itsneutral or no delivery position. Let it be assumed that the pump I06 isin operation, supplying pressure fluid through the line I I5 and valve II 6 to the space above the press piston head I23. The piston head I23and its piston rod I24 move downwardly, closing the press and engagingthe workpiece so that pressure is built up to the specified pressure of500 pounds per square inch.

When this pressure is reached, the servomotor piston 5| will move to theright (Figure 1), overcoming the thrust of the spring 14 and moving theshift ring I3 of the pump to its neutral or no delivery position. Thepump I06 will therefore temporarily hold the pressure in the pressingcylinder I2I at 500 pounds per square inch. Meanwhile, at the time thepress closed, its arm I28 closed the limit switch I64, thereby startingthe timing device I6I. After the expiration of the time period for whichthe timing device I60 is set, the latter closes the circuit, energizingthe operating coil I58 of the contactor I53, shifting its switch bladesI54 and I55 into a position to energize the solenoid I45. The latterthen shifts the valve rod I43 of the three-way valve I42 so as to admitpressure from the conduit I49 to the conduit I41, and thence into thecylinder bores 84 against the pistons 81.

The pistons 81 then move to the left (Figure compressing the coil spring14. This action causes the shift rod 33 to move to the left, under theincreased thrust of the coil spring 14, carrying with it the pump shiftring I3, shift rod 32 and servomotor piston head 5|. The pistons 81 cometo rest against the ends of the stop rods 95, the positions of which maybe adjusted by turning the hand wheel IOI, thereby regulating theadditional compression space upon the coil spring 14, and hence,adjusting the high pressure stage of thepump. The pressure of 500 poundsper square inch now standing in the conduit I50 is therefore no longersuflicient to overcome the increased thrust of the coil spring 14.Accordingly, the pump again delivers pressure fluid to cause the pistonI23 and its piston rod I24 to exert an increased pressing effect, untilthe pressure rises to a sufficient amount where it will again actagainst the annular piston area 60 and again shift the servomotor pistonhead 5I to the right, overcoming the increased thrust of the coil spring'14 and again moving the pump shift ring I3 to its neutral or nodelivery position. At this greater pressure, for example 2,500 poundsper square inch, the pump is again shifted to its neutral or no deliveryposition automatically and without the necessity for attention on thepart of the operator.

When the four-way valve I I6 is shifted to supply pressure fluid to theport I20 and retract the pressing piston I23, the limit switch I64 isopened and de-energizes the timing device I6I, in turn de-energizing andopening the contactor I53 and consequently de-energizing the solenoidI45. The three-way valve I42, therefore, shifts into a position closingofi the conduit I49 from communication with the conduit I41, andconnecting the latter to the exhaust conduit I46. The pressure is thusreleased from the righthand ends of the cylinder bores 84 (Figure 1) sothat the thrust of the coil spring 14 moves the yoke 10 and piston heads81 to the right to the positions shown in Figure 1. The electrical andhydraulic circuits are thus placed in readiness for the resumption ofanother pressing stroke, and the parts come to rest in the positionsshown in Figure 2.

In the circuit shown in Figure 2, the pressure fluid employed in thehydraulic circuit has also been utilized for shifting the pistons 81. Itwill be obvious, however, that pressure fluid from any source, such asair pressure, may be used to shift these piston heads. It is alsoobvious that the timing device I6I may be omitted, and is also obviousthat the three-way valve I42 may be shifted manually when the operatorwishes to apply the additional pressing pressure. Alternatively, thethree-way valve I42 may be shifted by some portion of the machine whenit reaches a predetermined position, such as directly by the press armI28.

The servomotor arrangement containing a plurality of annular pistonareas adapted selectively to be subjected to pressure fluid in thehydraulic circuit is disclosed and claimed in the copending applicationof Ernst et al, Serial No. 220,046, filed July 19, 1938 and which hasmatured into Patent No. 2,230,054, dated January 28, 1941. It will beobserved, however, that the servomotor would be operative for thepresent purpose with the employment of a single piston area instead ofthe more convenient plural piston arrangement shown in Figure 1.

The present invention finds an important application in plasticinjection molding machinery materials or compounds, it is founddesirable to inject the softened material into the mold and maintain itunder a moderate pressure for a certain time, while the material softensand partially conforms to the shape of the-mold.

After the expiration of this time, it is then found useful to apply amuch higher pressure tothe material to force it into the more intricatecorners or cavities of the mold. In the present invention, however,these two pressure stages may be severed and adjusted relatively to eachother throughout a wide range of pressures so as to adapt the inventionmost efliciently to the particular working conditions and materials.

It will be understood that I desire to comprehend within my inventionsuch modifications as come within the scope of the claims and theinvention.

Having thus fully described my invention, what I claim as new and desireto secure by Letters Patent is:

1. A method of molding work-pieces from plastic material comprisingsoftening the material,

and methods. With the use of certain molding injecting the material intoa mold by exerting hydraulic pressure on an injecting plunger, hold ingthe material in the mold at said pressure for a predetermined timeperiod, and thereafter increasing said hydraulic pressure acting uponsaid plunger, thereby applying a higher pressure to said material tofill out the mold.

2. A method of molding workpieces from plastic material comprisingsoftening the material to .render it plastic, injecting the softenedmaterial into a mold cavity by exerting a predetermined hydraulicpressure on an injecting plunger, maintaining said predeterminedpressure for a predetermined interval of time so as to maintainsubstantially the same pressure on the material in the mold cavity, atthe expiration of this time interval increasing said hydraulic pressureacting upon said plunger and maintaining said increased pressure for apredetermined time, thereby applying a relatively high pressure to thematerial to complete the molding operation, and thereafter releasing thepressure from the material.

WALTER ERNST.

